1. Field of the Invention
The present invention relates to a method and an apparatus for inspecting foreign matters in or on repeated micro-miniature patterns, in particular, to the method and the apparatus for use in inspecting or detecting minute or microscopic foreign matter(s) upon a surface of an object to be inspected, such as the repeated micro-miniature patterns which are formed on a semiconductor wafer, with high sensitivity.
2. Description of Related Art
With great advance in scale of integration and in miniaturization of circuitry patterns of a semiconductor integrated circuit (herein after, it is called only by “IC”) in recent years, circuit patterns being formed on it come to be in an order of 1 μm or less than that in width thereof. For producing such an IC with high productivity, it is necessary to detect particles or foreign matters attached on the surface of the wafer and to inspect or examine sizes, shape, feature and property thereof, so as to quantitatively obtain cleaning degrees in various apparatuses and/or processes for producing the semiconductor, and thereby to manage production process appropriately. Therefore, conventionally, the detection and/or inspection of the foreign matters on wafers was applied to, with methods and/or apparatuses for inspection of foreign matters attached or adhered to the wafers, as works in IC production facilities in factories, so as to manage the production processes appropriately.
The conventional inspection apparatuses for inspection of foreign matters on wafers can be divided roughly into two categories. A first one is a patterned wafer inspection apparatus of an image comparison type (hereinafter, it is called by a “visual inspection apparatus”), in which the comparison is carried out between the image under a bright field of an illumination and a reference pattern which is previously stored. A second one is a patterned wafer inspection apparatus of such type (hereinafter, it is called by “an inspection apparatus”) that it detects scattered light in a dark field under an inclined illumination, acknowledges existence of defects or foreign matters, and determines coordinate positions and the number thereof, by means of the coordinates obtained at the time of detection of the scattered light.
Further, an example of such apparatuses for inspection of defects on the wafers is described on pages from 97 to 116 of “Nikkei Micro-devices, March, 1997”, which is published by Nikkei Business Publication, Inc.
The visual inspection apparatus mentioned above has an advantage that it shows high accuracy in inspection; however, it has drawbacks that throughput thereof is low and that it is expensive in price. And, since an image or visual data can be obtained by the visual inspection apparatus, it enables a so-called review (i.e., a confirmation or an inspection by means of the image, visually). However, by the inventors of the present invention, it is made clear that, in the visual inspection apparatus, information not only necessary but also unnecessary to be reviewed are also provided too much, in comparison with the number of pieces of the wafers to be inspected, including such as for a microscopic defect, therefore, a probability of obtaining fatal or killer defects is very low and there is a drawback that an efficiency of the review comes to be low.
On the contrary, though the inspection apparatus mentioned above has a drawback that it is lower than that of the visual inspection apparatus in the accuracy, it has an advantages that the throughput of it is higher, comparing to that of the visual inspection apparatus, and that it is also lower in the price thereof. And, since the data which can be obtained from the inspection apparatus includes only the coordinate positions of the defects in a surface area of the wafer, as well as an intensity of the scattered light, therefore, it is impossible to obtain information relating to the size(s) of the defect (i.e., a diameter of the particle) and the shape thereof (even if possible, within a degree to classify it into S (small), M (medium) and L (large) in the size, roughly). Accordingly, for obtaining the information concerning to those in more detail, there is a necessity of using the inspecting apparatus of analyzer type, such as the visual inspection apparatus as mentioned above or an another kind of inspection apparatus, such as a SEM (Scanning Electron Microscope) which, however, takes a long time for inspection or analysis and expensive in the price.